Was there a breeze?


Shimming the sight will not change the walk back tune if you are doing it correctly.Because the 20 yard pin is the only pin used for walk back.


The reason the bow shoots to the right is because you are canting the bow.You apparently don't have or use a the level.OR,it isn't set square with the pins.

If shimming the sight has the bow comfortable in your hands and has the pins vertical,then leave it and forget it.